40 BOTANICAL GAZETTE ■ [jul'y 



cytoplasm of the inner wall cells, which even at this stage contain a 

 little starch; the outer wall cells contain considerable at this time. 

 The tapetal cytoplasm was not observed to contain any starch until 

 after the walls have broken down. The walls themselves are from 

 the first very delicate, but are sharp and distinct when properly 

 stained, so that there can be no mistake as to their presence. In this 

 respect Ophioglossum seems to differ from B. virginianum, whose 

 tapetal cells, as described by Stevens, are delimited by a plasmatic 

 membrane only. Cardiff, who studied, the same species, does not 

 mention this circumstance, and Beer calls attention to the fact that 

 it is not true in Helminthostachys. The nuclei are about 20/* in 



■J rt 



diameter, but vary somewhat both in size and shape. They stain 

 rather deeply and are generally not otherwise distinguishable from 

 the nuclei of the wall cells. 



When the mother-cell stage is reached, the tapetum is at least two- 

 layered throughout and its w^alls have become very thin and about 

 this time have begun to break dow^n. The cytoplasm of the neighbor- 

 ing tapetal cells mingles and forms a plasmodium, as described by 

 Cardiff for Botrychium. In Botr}^chium as well as in Helminthos- 

 tachys the tapetal cells are elongated radially, while in Ophioglos- 

 sum they are flat and tabular, the radial diameter being the shortest. 



bssum also differs from 



from 



ossum 



than in the other genera. This is probably correlated with the fewer 

 layers and with the fact that in Botrychium the cells are frequently 

 binucleate. Too few preparations at just the stage when the walls are 

 breaking down were seen to make sure that binucleate cells do not 

 occur, but none were seen. 



Bower and others have stated that at this time some of the mother 

 cells break down and contribute to the tapetal plasmodium. This is 

 denied by Cardiff for Botrychium, and by Beer for Helminthos- 



tachys, No 



'b served in 



Ophioglossum, but the number of preparations of just this age 

 observed w^ere too few to justify the statement that it never occurs. 

 Mother cells which did not appear normal were found in two or three 

 preparations, but in each case they occurred in sporangia that were 



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